In many printing systems, it is common practice to develop a hardcopy of an image by using a photoconductive surface. The photoconductive surface is selectively charged with a latent electrostatic image having image and background areas. For example, a liquid developer comprising charged toner particles in a carrier liquid can be brought into contact with the selectively charged photoconductive surface. The charged toner particles adhere to the image areas of the latent image while the background areas remain clean. A hardcopy material (e.g. paper or other print substrate) is brought directly or indirectly into contact with the photo-conductive surface in order to transfer the latent image. Variations of this method utilize different ways for forming the electrostatic latent image on a photoreceptor or on a dielectric material.
Typically, the liquid developer comprises a thermoplastic resin as the basis for the toner particles, and a non-polar liquid as a carrier liquid in which the toner particles are dispersed. Generally, the toner particles contain a colorant such as a pigment. A charge director, also called charge control agent or imaging agent, is also added to the dispersion to induce charge on the particles.
However, such printing systems may suffer from print defects such as streaks which are reflected as variations in the optical density within the printed area. As such, improvement of such printing systems through ongoing research and developmental efforts continue to be sought.